At least 20 people were killed in a shooting outside the Mandalay Bay Resort and Casino after a gunman unloaded hundreds of rounds of ammo on a Las Vegas country music festival on Sunday night. Witnesses said shots were fired from an elevated hotel position. More than 100 people were wounded. There were 30,000 people in attendance at the event.

The Strip has been completely shut down after the sniper opened fire on the Route 91 Harvest country music festival from the 32nd floor of the Mandalay Bay resort and casino, located across a junction from the event. Police confirmed that one suspect had been killed, and said at 12:38am that they believed there were no more shooters. It’s not clear how many shooters there had been.

Those listening to police scanners reported that the shooter was killed after cops breached a room on the 32nd floor of the Mandalay Bay. SWAT teams were seen heading towards the resort in armored vehicles earlier.

Police said they are also seeking a woman they named as Marilou Danley, described as a companion of the suspect.

According to LVMPD Sheriff Joe Lombardo, Off-duty police officers are among the dead. Their identities have not been released. Two police officers are also being treated for injuries with one officer in critical condition and the other has minor injuries.

There had been reports of other incidents at different locations along the Las Vegas strip, but police say they believe the dead suspect acted alone.

University Medical Center spokeswoman Danita Cohen said the Las Vegas hospital is taking in “several” people with gunshot wounds, adding that 14 of the wounded were in a critical condition.

Many hotels on the Las Vegas strip close to the scene remain on lockdown. Parts of Las Vegas Boulevard were shut as armed police arrived at the scene of the attack.

People have been sheltering in hotels, restaurants and at Las Vegas McCarran airport. Some flights were diverted after news of the incident